ML071380230
| ML071380230 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 07/20/2007 |
| From: | Tam P NRC/NRR/ADRO/DORL/LPLIII-1 |
| To: | O'Connor T Nuclear Management Co |
| tam P, NRR/ADRO/DORL, 415-1451 | |
| Shared Package | |
| ML071930105 | List: |
| References | |
| TAC MD4095 | |
| Download: ML071380230 (17) | |
Text
July 20, 2007 Timothy J. OConnor Site Vice President Monticello Nuclear Generating Plant Nuclear Management Company, LLC 2807 West County Road 75 Monticello, MN 55362-9637
SUBJECT:
MONTICELLO NUCLEAR GENERATING PLANT - ISSUANCE OF AMENDMENT RE: LOW-PRESSURE COOLANT INJECTION SYSTEM LOOP SELECT LOGIC TIME DELAY FUNCTIONS (TAC NO. MD4095)
Dear Mr. OConnor:
The Commission has issued the enclosed Amendment No. 151 to Renewed Facility Operating License No. DPR-22 for Monticello Nuclear Generating Plant (MNGP), in response to your application dated January 29, 2007, as supplemented on June 5, 2007.
The amendment revised Table 3.3.5.1-1 of the technical specifications for three low-pressure coolant injection loop select logic functions. The surveillance of these three functions was previously required to be performed every 92 days. The amended requirement requires a channel calibration and logic system functional test, respectively, every 24 months. In addition, the allowable values associated with these three functions are changed to match the extended surveillance interval.
A copy of our related safety evaluation is also enclosed. The Notice of Issuance will be included in the Commission's biweekly Federal Register notice.
Sincerely,
/RA/
Peter S. Tam, Senior Project Manager Plant Licensing Branch III-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-263
Enclosures:
- 1. Amendment No. 151 to DPR-22
- 2. Safety Evaluation cc w/encls: See next page
Timothy J. OConnor July 20, 2007 Site Vice President Monticello Nuclear Generating Plant Nuclear Management Company, LLC 2807 West County Road 75 Monticello, MN 55362-9637
SUBJECT:
MONTICELLO NUCLEAR GENERATING PLANT - ISSUANCE OF AMENDMENT RE: LOW-PRESSURE COOLANT INJECTION SYSTEM LOOP SELECT LOGIC TIME DELAY FUNCTIONS (TAC NO. MD4095)
Dear Mr. OConnor:
The Commission has issued the enclosed Amendment No. 151 to Renewed Facility Operating License No. DPR-22 for Monticello Nuclear Generating Plant (MNGP), in response to your application dated January 29, 2007, as supplemented on June 5, 2007.
The amendment revised Table 3.3.5.1-1 of the technical specifications for three low-pressure coolant injection loop select logic functions. The surveillance of these three functions was previously required to be performed every 92 days. The amended requirement requires a channel calibration and logic system functional test, respectively, every 24 months. In addition, the allowable values associated with these three functions are changed to match the extended surveillance interval.
A copy of our related safety evaluation is also enclosed. The Notice of Issuance will be included in the Commission's biweekly Federal Register notice.
Sincerely,
/RA/
Peter S. Tam, Senior Project Manager Plant Licensing Branch III-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-263
Enclosures:
- 1. Amendment No. 151 to DPR-22
- 2. Safety Evaluation cc w/encls: See next page DISTRIBUTION:
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RidsRgn3MailCenter RidsNrrDirsItsb BParks CDoutt PLoeser GSingh Package Accession Number: ML071930105 Amendment Accession Number: ML071380230 Tech. Spec. pages Accession Number: ML071930119 OFFICE LPL3-1/PM LPL3-1/ LA SBWB/BC APLA/BC EICB/BC OGC LPL3-1/(A)BC NAME PTam THarris GCranston*
MRubin*
WKemper*
JBonanno LRaghavan for TTate DATE 7/12/07 7/12/07 4/3/07*
3/21/07*
6/27/07*
7/17/07 7/20/07 OFFICIAL RECORD COPY
- Safety evaluation input transmitted by memo on the date indicate
NUCLEAR MANAGEMENT COMPANY, LLC DOCKET NO. 50-263 MONTICELLO NUCLEAR GENERATING PLANT AMENDMENT TO RENEWED FACILITY OPERATING LICENSE Amendment No. 151 License No. DPR-22 1.
The Nuclear Regulatory Commission (the Commission) has found that:
A.
The application for amendment by Nuclear Management Company, LLC (the licensee), dated January 29, 2007, as supplemented on June 5, 2007, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act), and the Commission's rules and regulations set forth in 10 CFR Chapter I; B.
The facility will operate in conformity with the application, the provisions of the Act, and the rules and regulations of the Commission; C.
There is reasonable assurance (i) that the activities authorized by this amendment can be conducted without endangering the health and safety of the public, and (ii) that such activities will be conducted in compliance with the Commission's regulations; D.
The issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public; and E.
The issuance of this amendment is in accordance with 10 CFR Part 51 of the Commission's regulations and all applicable requirements have been satisfied.
2.
Accordingly, the license is amended by changes to the Technical Specifications as indicated in the attachment to this license amendment, and paragraph 2.C.2 of Facility Operating License No. DPR-22 is hereby amended to read as follows:
Technical Specifications The Technical Specifications contained in Appendix A, as revised through Amendment No. 151 are hereby incorporated in the license. NMC shall operate the facility in accordance with the Technical Specifications.
3.
This license amendment is effective as of its date of issuance and shall be implemented within 60 days of issuance.
FOR THE NUCLEAR REGULATORY COMMISSION
/RA by L. Raghavan/
Travis L. Tate, Acting Chief Plant Licensing Branch III-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
Attachment:
Changes to the Facility Operating License and Technical Specifications Date of Issuance: July 20, 2007
ATTACHMENT TO OPERATING LICENSE AMENDMENT NO. 151 RENEWED FACILITY OPERATING LICENSE NO. DPR-22 DOCKET NO. 50-263 Replace the following page of Renewed Facility Operating License DPR-22 with the attached revised page. The revised page is identified by amendment number and contains a marginal line indicating the area of change.
REMOVE INSERT Page 3 Page 3 Replace the following pages of Appendix A (Technical Specifications) with the attached revised pages. The revised pages are identified by amendment number and contain marginal lines indicating the areas of change.
REMOVE INSERT 3.3.5.1-5 3.3.5.1-5 3.3.5.1-6 3.3.5.1-6 3.3.5.1-8 3.3.5.1-8 3.3.5.1-9 3.3.5.1-9 2.
Pursuant to the Act and 10 CFR Part 70, NMC to receive, possess, and use at any time special nuclear material as reactor fuel, in accordance with the limitations for storage and amounts required for reactor operations, as described in the Final Safety Analysis Report, as supplemented and amended, and the licensees filings dated August 16, 1974 (those portions dealing with handling of reactor fuel) and August 17, 1977 (those portions dealing with fuel assembly storage capacity);
3.
Pursuant to the Act and 10 CFR Parts 30, 40 and 70, NMC to receive, possess, and use at any time any byproduct, source and special nuclear material as sealed neutron sources for reactor startup, sealed sources for reactor instrumentation and radiation monitoring equipment calibration, and as fission detectors in amounts as required; 4.
Pursuant to the Act and 10 CFR Parts 30, 40 and 70, NMC to receive, possess, and use in amounts as required any byproduct, source or special nuclear material without restriction to chemical or physical form, for sample analysis or instrument calibration or associated with radioactive apparatus or components; and 5.
Pursuant to the Act and 10 CFR Parts 30 and 70, NMC to possess, but not separate, such byproduct and special nuclear material as may be produced by operation of the facility.
C.
This renewed operating license shall be deemed to contain and is subject to the conditions specified in the Commissions regulations in 10 CFR Chapter I and is subject to all applicable provisions of the Act and to the rules, regulations, and orders of the Commission, now or hereafter in effect; and is subject to the additional conditions specified or incorporated below:
1.
Maximum Power Level NMC is authorized to operate the facility at steady state reactor core power levels not in excess of 1775 megawatts (thermal).
2.
Technical Specifications The Technical Specifications contained in Appendix A, as revised through Amendment No. 151, are hereby incorporated in the license. NMC shall l
operate the facility in accordance with the Technical Specifications.
3.
Physical Protection NMC shall implement and maintain in effect all provisions of the Commission-approved physical security, guard training and qualification, and safeguards contingency plans including amendments made pursuant to provisions of the Miscellaneous Amendments and Search Renewed License No. DPR-22 Amendment No. 1 thru 151
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION FOR AMENDMENT NO. 151 TO RENEWED FACILITY OPERATING LICENSE NO. DPR-22 NUCLEAR MANAGEMENT COMPANY, LLC MONTICELLO NUCLEAR GENERATING PLANT (MNGP)
DOCKET NO. 50-263
1.0 INTRODUCTION
By letter dated January 29, 2007 (Accession No. ML070300053), as supplemented by letter dated June 5, 2007 (Accession No. ML071570069), Nuclear Management Company, LLC (the licensee) submitted an application for amendment. The licensee proposed to amend the MNGP Technical Specifications (TSs) Section 3.3.5.1, Emergency Core Cooling Instrumentation, to extend surveillance test intervals (STls) as indicated in Table 3.3.5.1-1 for the following low-pressure coolant injection (LPCI) loop select logic functions:
2.k. Reactor Steam Dome Pressure - Time Delay Relay (Break Detection) 2.1. Recirculation Pump Differential Pressure - Time Delay Relay (Break Detection) 2.m. Recirculation Riser Differential Pressure - Time Delay Relay (Break Detection)
The surveillance of these three functions are currently performed in accordance with Surveillance Requirements (SRs) 3.3.5.1.2 and 3.3.5.1.4, which respectively require a channel functional test and channel calibration every 92 days. The licensee proposed to replace these SRs with SRs 3.3.5.1.7 and 3.3.5.1.9, requiring a channel calibration and logic system functional test, respectively, every 24 months. In addition, the licensee proposed to revise the allowable values associated with these three functions to match the longer surveillance intervals. The Nuclear Regulatory Commission (NRC) staff had previously found acceptable (Amendment No. 149, dated January 18, 2007; Accession No. ML063550429) a one-time extension of the surveillance interval by 48 days on the basis that performance of the required surveillance at power would subject the plant to transients, and was therefore an unnecessary burden on the licensee.
The licensee's supplement dated June 5, 2007, provided additional information that clarified the application, did not expand the scope of the application as originally noticed, and did not change the NRC staff's original proposed no significant hazards consideration determination as published in the Federal Register on March 13, 2007 (72 FR 11391).
2.0 REGULATORY EVALUATION
SRs are required to be in the TS under the provisions of paragraph (c)(3) of Section 36 to Part 50 of Title 10 of the Code of Federal Regulations (10 CFR 50.36(c)(3)). SRs are in the form of testing, calibration, or inspection to assure that the necessary quality of systems and components is maintained, that facility operation will be within safety limits, and that the limiting conditions for operation will be met.
MNGP was licensed and constructed prior to the implementation of 10 CFR Part 50, Appendix A, "General Design Criteria." Section 1.2 of the MNGP Updated Safety Analysis Report (USAR) lists the principal design criteria (PDC) for the design, construction, and operation of the plant and Appendix E of the USAR provides a plant comparative evaluation of the PDCs to the then proposed 70 Atomic Energy Commission (AEC) design criteria.
Specifically:
AEC Criterion 38, Reliability and Testability of Engineered Safety Features - This states that [a]ll engineered safety features shall be designed to provide a high functional reliability and ready testability. In determining the suitability of a facility for proposed site, the degree of reliance upon and acceptance of the inherent and engineered safety afforded by the systems, including engineered safety features, will be influenced by the known and the demonstrated performance capability and reliability of the systems, and by the extent to which the operability of such systems can be tested and inspected where appropriate during the life of the plant.
AEC Criterion 46, Testing of Emergency Core Cooling System Components - This requires that design provisions are made so that active components of the emergency core cooling systems, such as pumps and valves, can be tested periodically for operability and required functional performance.
The NRC staff found that the licensee has identified the appropriate AEC criteria, and found those AEC criteria analogous to General Design Criteria (GDC) 36, "Inspection of Emergency Core Cooling System," and GDC 37, "Testing of Emergency Core Cooling System,"
respectively, as currently set forth in 10 CFR Part 50, Appendix A.
3.0 TECHNICAL EVALUATION
In a General Electric boiling-water reactor (BWR) 3, such as MNGP, the LPCI system is designed so that the core is adequately cooled after a loss-of-coolant accident (LOCA). The LPCI system operates in conjunction with the high-pressure coolant injection (HPCI) system, the automatic depressurization system (ADS), and the core spray (CS) system to achieve this goal.
The LPCI system is designed to operate at low pressure and high flow to reflood the reactor core to at least two-thirds core height and to maintain this level. It operates after the reactor pressure vessel has depressurized. Inadvertent alignment and actuation of the LPCI system while the reactor is at pressure could result in an interfacing systems LOCA. At MNGP, the LPCI system uses the residual heat removal pumps to draw suction from the suppression pool and discharges water to one of the recirculation loops. A logic system in place is designed to detect the difference in pressure between the two loops, which would be indicative of a recirculation line break, and select the recirculation loop with high pressure (i.e., the unbroken loop) for discharge. Three time delay relays are provided in the logic system to provide for detection of a possible recirculation line break. Together, the time delay relays contribute to approximately three seconds of delay in the LPCI initiation sequence.
3.1 Evaluation of the Licensees Reason for the Proposed Amendment On June 5, 2006, the MNGP TSs document was converted to the BWR/4 Improved Technical Specifications (ITS) format, which contains a provision that requires surveillance testing and calibration of the LPCI loop select logic on a quarterly basis. The logic system at MNGP is testable in conformance with the specified design criteria; however, it is not designed to be tested online (i.e., while the reactor is at power). The licensee identified four possible scenarios (see Section 5.1 of the licensees January 29, 2007, application) that could lead to plant transients if the LPCI loop select logic surveillance and calibration were performed online as required by the TSs.
The licensee stated that the LPCl loop select logic time delay relays were demonstrated functional during the once-a-cycle Emergency Core Cooling System (ECCS) performance testing during refueling outages. The licensee contends that [o]n-line testing of these time delay relays poses an unacceptable risk for an inadvertent plant transient resulting in an unnecessary challenge to safety systems. To support this statement, the licensee identified four possible scenarios resulting from inadvertent erroneous testing, that could lead to plant transients if the LPCI loop select logic surveillance and calibration were performed online as required by the TSs. The licensee further stated that:
The LPCl loop select logic is not designed to be tested on-line. Testing of these time delay relay functions has not been performed on-line at the MNGP or at any other Boiling-Water Reactor (BWR) to the best of our knowledge. NMC inappropriately specified a quarterly (92 day) surveillance interval for testing these LPCl loop select time delay relays during ITS development. ITS Surveillance Requirements (SR) 3.3.5.1.2 and 3.3.5.1.4 require performance of a CHANNEL FUNCTIONAL TEST and a CHANNEL CALIBRATION, respectively, every 92 days, which will require testing of the LPCl loop select logic on-line.
To rectify the inappropriate SRs, the licensee proposed that the SRs for the Channel Functional Test and Channel Calibration Test be extended to 24 months in lieu of the current 92 days.
The NRC staff reviewed the licensees stated reasons for the need for the amendment, and agrees that the proposed amendment to the TSs will reduce unnecessary burden on the licensee, and will eliminate the possibility of the four undesirable scenarios identified by the licensee in that performance of the TS-required surveillance tests could subject MNGP to unnecessary transients. The NRC staffs detailed evaluation is documented in Sections 3.2 and 3.3 below.
3.2 Evaluation of the Licensees Risk Insights The proposed amendment is not risk-informed, but is based on deterministic analysis and current NRC staff positions. However, the licensee did provide risk insights from a plant-specific MNGP probabilistic risk assessment (PRA) of the proposed change. Thus, the scope of the NRC staffs review was limited to the evaluation of the risk impact and potential risk implications of the proposed amendment per the guidance of NUREG-0800, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants, Chapter 19, Use of Probabilistic Risk Assessment in Plant-Specific, Risk-Informed Decisionmaking, Appendix D, Use of Risk Information in Review on Non-Risk-Informed License Amendment Requests.
Appendix D provides review and assessment guidance on whether a special circumstance exists such that the normal presumption of adequate protection is no longer met by compliance with existing regulatory requirements for license amendment requests that are not risk-informed. Per the guidance given in Appendix D, the NRC staff used the risk-informed decisionmaking process in Regulatory Guide (RG) 1.174, An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis, in its review. Although the RG 1.174 acceptance guidelines by themselves do not constitute a definition of adequate protection, they do provide an appropriate set of criteria to be used in the initial process of evaluating adequate protection and provide a basis for finding that there is reasonable assurance of adequate protection.
The licensee stated that the performance of a quarterly channel functional test and calibration for the LPCI loop select logic time delay relays is required based on incorrectly adopting a 92-day surveillance interval when the MNGP TSs document was converted to the ITS format.
Specifically, the licensee stated that LPCI loop select logic was not designed to be tested on-line, testing on-line presents an unacceptable risk for inadvertent plant transient(s) resulting in unnecessary challenges to safety systems.
The licensee modified the MNGP average maintenance PRA model to reflect the increased LPCI loop select logic time delay relay failure rate for the increased 24-month surveillance test interval. In addition, the licensee conservatively assumed that the loop select logic always selects the wrong recirculation loop for injection. The LPCI loop select logic is only required for a recirculation line break LOCA. The importance of the loop select feature is limited by the LPCI recirculation loop LOCA event break sizes. For the higher probability break size of less than 3 inches, the licensee stated that adequate core cooling is maintained with the assumed failure of the LPCI loop select logic to select the unbroken recirculation loop. For breaks larger than 3 inches, the assumed failure of the LPCI loop select logic to select the unbroken recirculation loop will result in LPCI failure for recirculation LOCA events. Therefore, the impact is limited to lower probability medium and large-break LOCAs on the recirculation line.
Based on the above, the licensee estimated a change in core damage frequency of less than 1.4E-8/year for the proposed extension of the time delay relay surveillance test interval from 92 days to 24 months. This increase is considered very small per RG 1.174. Although the 24-month surveillance test interval is a nominal value (i.e, the TS allows up to a 25 percent extension), a TS-allowed extension is expected to have only a minimal impact on the licensees conclusion. The licensee also stated that the change in large early release frequency remains below the very small acceptance guideline of RG 1.174. As a verification of the licensees calculations, the NRC staff performed limited confirmatory calculations using a simplified model of MNGP. The NRC staff review assumed similar relay failure rates over a range of surveillance test intervals and assumed that a failure of loop select logic would fail the LPCI system. The NRC staffs risk estimates are comparable with the licensees. Therefore, the NRC staff concludes that the licensees proposed extension for the time delay relay surveillance test interval does not invoke special circumstances.
The licensee did not indicate that the risk impacts played any role in its basis for the acceptability of this proposed amendment. The licenses application did not address the key principles of risk-informed decisionmaking as presented in RG 1.174 and the NRC staff did not complete the full scope of risk review that would be required of a risk-informed submittal.
Although RG 1.174 risk acceptance guidelines were used in evaluating the licensees amendment request, the NRC staff did not review the amendment request based on the limited risk information available. In addition, the NRC staff did not evaluate traditional engineering insights such as maintenance recommendations, surveillance or maintenance history, setpoint methodology, or related topical reports (not specific to PRA analysis).
The NRC staff finds that the licensees proposed increase in the LPCI loop select logic time delay relay surveillance test intervals to 24 months does not reveal an unforseen hazard or a substantially greater potential for a known hazardous event to occur such that adequate protection would be in question. The NRC staff did not identify special circumstances that, if reviewed on a risk-informed basis, would warrant attaching conditions to or denying the proposed amendment. This conclusion is based on the very small increase in core damage frequency and large early release frequency (i.e., the increase in risk is within the RG 1.174 acceptance guidelines) for the proposed change. The estimated risk impacts are very small and should not significantly influence the overall results of the licensees deterministic analysis.
3.3 Evaluation of Instrumentation Issues The licensee proposed a permanent time extension to the LPCI loop select logic surveillance requirements for Channel Functional Test and Channel Calibration Test from 92 days to a nominal 24-month interval. Other than that, this proposed change to the TSs does not involve any change to the design of the LPCI system. The testability of the LPCI system is maintained, and the existing surveillance requirements are being extended in line with the current SRs of other similar plants for the same function (i.e. BWR 3 plants requiring LPCI loop select logic testing).
The NRC staff surveyed the TS for LPCI select logic time delay relays for Quad Cities Units 1 and 2, and Dresden Units 2 and 3, and found that the channel calibration and logic system functional checks are required to be performed at a frequency of 24 months. For Pilgrim 1, the requirement specifies that simulated automatic testing for the LPCI is to be performed only once per operating cycle (i.e., 24 months). The NRC staff agrees that the proposed changes to the MNGP TSs would preclude the potential inadvertent transients that could be caused by performance of the 92 day surveillance tests.
In the application, the licensee stated that the LPCI loop select time delay relay functions are not limiting safety system setpoints (LSSS) that protect a safety limit (SL), and consequently TSTF-493 requirement to Clarify Application of Setpoint Methodology for LSSS Functions does not apply. During NRC staffs review of Amendment No. 143, dated September 30, 2005 (Accession No. ML052700252), regarding implementation of 24-month fuel cycle, the licensee identified the parameters for which LSSS have been assigned. The parameters associated with LPCI loop select logic time delay relays, even though safety-related, were not cited as SL or LSSS in that review.
The NRC staff previously approved (Amendment No. 149, dated January 18, 2007, Accession No. ML063550429) a one-time extension of the subject LPCI loop select logic surveillance interval from 92 days to 140 days. This extension allowed the previous (the only one required since implementation of ITS) surveillance be performed during the spring 2007 outage. In the safety evaluation supporting Amendment No. 149, the NRC staff noted the following:
The licensee stated that the proposed surveillance test interval increase would result in performance of surveillance tests in accordance with old interval requirements (i.e., in the former custom TSs) that were in place prior to the licensees implementation of the ISTS. The licensee further stated that these surveillance tests assured operability of the LPCI loop select logic system time-delay relays. The NRC staff requested that the licensee provide documentation of the three most recent surveillances that showed that the LPCI loop select logic system time delay relays were functional. The licensee provided this documentation in its December 28, 2006, letter; the NRC staff reviewed the documentation and concluded that the recent test results demonstrated that the LPCI loop select logic system time delay relays remain in functional condition.
The NRC staff concluded, based on the recent test results, that surveillance performed under the proposed surveillance test interval increase will continue to demonstrate the functionality of the subject time-delay relays.
The data provided by the licensee indicated that the relays were functioning properly. Using the guidance of Generic Letter (GL) 91-04, the licensee had recalculated the drift values. Drift data was based on the HPCI steamline flow - high time delay relay, which has an adjustable range of 0.55 to 15 seconds with a setpoint of 4 seconds. This relay is similar to the relays used for the LPCI loop select logic relays except the adjustable time is 0.55 to 15 seconds as opposed to the 0.15 to 3.0 seconds adjustable time delay for the LPCI loop select logic relays. Both relays are nuclear-qualified Agastat model ETR14D3. In a request for additional information (RAI) dated April 17, 2007 (Accession No. ML071020188), the NRC staff requested the licensee to provide the justification for using the drift data from ETR14D3B for the ETR14D3A. In its June 5, 2007, letter, the licensee stated that the Agastat ETR series time delay relays are the nuclear-qualified version of the Agastat TR time delay relays. As indicated on the data sheet provided in Enclosure 3, they are of an electromechanical design with a solid-state timing network and are available in eight timing ranges from Range A (0.15 to 3 seconds) to Range I (2 to 60 minutes). As further discussed in the response to RAI ltem 6, there is no difference, other than a change in a resistor value to control the timing range, which would affect the performance of the various time ranges within the ETR series of time delay relays. Since there are no significant differences between the ETR series of time delay relays, and the LPCl loop select time delay relays (Agastat model ETR14D3A) are located in the same environment within the Cable Spreading Room (as the Agastat model ETR14D3Bs), the licensee determined that the analyzed drift values for the ETR14D3B time delay relays could be applied to provide a conservative estimate of the drift that the ETR14D3A relays will experience. The NRC staff has reviewed the data sheet for the Agastat Nuclear Qualified Control Relays - Series EGP/EML/ETR, provided as an Attachment to the June 5, 2007, letter, and found that all the relays in all three series are of the same construction and the same test report applies to all three series of relays. The timing circuit is comprised of a resistance-capacitance circuit. ETR series relays are equipped with a variable potentiometer to adjust the time delay.
Based on the similarity in design and the type of relays, the licensees explanation is logical and is acceptable to the staff. The drift data for this time delay relay for the 92-day drift uncertainty is +/-9.9 percent of setpoint. The licensee noted that based on past performance, the drift value for these relays was not found to be time-dependent and, thus, the drift did not need to be calculated on linear time basis. Based on this justification, the licensee has assumed that the 30-month drift value is moderately time-dependent (drift for each calibration time period considered as independent and random) and extrapolated to 30-months by multiplying the 92 day drift value by the square root of the time periods. This resulted in a calculated 30-month drift of approximately +/-31.4 percent.
The licensee plans to use 10.9 percent value of the setpoint for the as-found tolerance, and has provided the following justification in support of this value:
To calculate the As Found Tolerances, the drift uncertainty from the HPCl steamline flow - high time delay relays (Agastat model ETR14D3B) was treated as non-time dependent. The drift uncertainty for the extended (30-month) calibration interval was determined by increasing the tolerance interval to the 99 percent /95 percent level. This resulted in a 30-month drift uncertainty of approximately +/-10.9 percent of setpoint.
This proposed as-found tolerance of 10.9 percent is conservative as compared to the 30-month drift value of 31.4 percent, and is, therefore, acceptable to the NRC staff.
In order to ensure that the performance of the relays is enveloped by the assumptions made in the drift/setpoint calculations, the licensee has committed to add the LPCI loop select logic time delay relays to the Instrument Trending Program. Relays found outside the as-found tolerance will be entered in the MNGP Corrective Action Program (CAP) to ensure that any negative trend will be identified, documented, and appropriate actions taken per the Monticello Methodology Summary and Compliance With GL 91-04 (see licensees submittal dated June 30, 2004; Accession No. ML042040159). The trending program will address the TSs setpoints that exceed the expected drift for the instruments. The trending program also requires that any time a setpoint value is found to exceed the expected drift, an additional evaluation will be performed to ensure the instruments performance is still enveloped by the assumptions in the drift or setpoint analysis. The licensees instrument operability determination will be based on this licensee evaluation (page 2 of the June 5, 2007, submittal):
LOCA analysis results indicate that the limiting large-break and single-failure combination for the MNGP is the maximum recirculation suction line break with battery failure for nominal assumptions and with LPCl injection valve failure for 10 CFR Part 50 Appendix K assumptions. The most limiting small recirculation line break is the 0.07 ft2 recirculation line suction break for nominal assumptions and the 0.08 ft2 recirculation line suction break for Appendix K assumptions. For the four other evaluated non-recirculation line break LOCA events (feedwater, core spray, and a main steamline break (both in and outside containment)) the ECCS performance was evaluated. For these non-recirculation loop LOCA events, success of the loop select logic to properly pick the unbroken recirculation loop is not required and the cases were non-limiting.
LOCA with a loss of offsite power is the most limiting case for the large LOCA event because of the additional time required for the diesel generator to start up and come up to speed. In the accident analysis (Monticello Updated Safety Analysis Report, Table 14.7-12) credit is taken for a time delay of 15 seconds for the diesel generator to start up and start accepting loads. The LPCI loop select control logic is powered from the 125-Vdc (battery backed) power supply and will function while the diesel generator is coming up to speed. With loss of offsite power, both recirculating pumps trip at the beginning of the event. The timer to detect which recirculating pump is running (time delay of #0.75 seconds) initiates without waiting for the diesel generator to start and come up to speed. For single-loop operation, the reactor pressure must fall below 900 psig before the LPCI pump can start. The large-break LOCA analysis assumes that it takes approximately 4 seconds for the reactor pressure to drop to 900 psig, so a time of approximately 11 seconds (difference between the time of 15 seconds for the diesel generator to start and 4 seconds for the reactor pressure to fall below 900 psig) is available for the time delay relays to complete the LPCI loop select logic. This provides a large margin for completion of the LPCI loop select time delay relays to perform their function. For LPCI injection to take place, power must also be available at the LPCI injection valve, and the LPCI injection valve must be open. The time assumed for the valve to open is 35 seconds. Actual LPCI flow will start only after the reactor pressure drops below the LPCI pump shutoff head of 350 psig.
For a limiting small-break recirculation line break LOCA, the reactor pressure depressurizes much more slowly and the LPCI injection takes place at approximately 450 seconds into the event. Hence, a much longer time is available for the LPCI loop select time delay relays to perform their function.
3.3.1 Summary of Instrumentation Issues The 24-month nominal (30 month calculated) drift is approximately 31.4 percent. The as-found tolerance is established at 10.9 percent. Further, the drift values have been established in line with the guidance of GL 91-04. The licensee has applied the NRC-approved (November 6, 1995, NRC letter, from Bruce Bogger to Robert A. Pinelli) GE instrument Setpoint Methodology (NEDC-31336-P-A), to determine the allowable value (AV) for the LPCl loop select time delay relays. The method used to calculate the AV is similar to ISA-S67.04, Method 2. However, the GE lnstrument Setpoint Methodology includes additional error terms not included in ISA Method
- 2. With the inclusion of these additional error terms, the resulting AV is more conservative from the perspective of protecting the analytical limit (AL).
3.4 Evaluation of the Proposed TS Changes The licensee proposed to extend the LPCI loop select logic surveillance from the current 92 days to 24 months. The proposed change of the STI does not involve any modification to the design of the LPCI system. Because the testability of the LPCI system is not being changed, and the SRs are not being deleted, the NRC staff concludes that the proposed amendment will not render the LPCI system into noncompliance with 10 CFR 50.36(c)(3), and the LPCI system will continue to comply with the criterion identified in Section 2.0.
The licensee stated that the proposed STI increase would result in performance of surveillance tests in accordance with requirements that were in place prior to the licensee's implementation of the STS. The licensee further stated that these surveillance tests assured operability of the LPCI loop select logic system time delay relays. In a letter dated December 28, 2006 (Accession Number ML063630253), the licensee provided test data that showed that the LPCI loop select logic time delay relays were functional. The NRC staff reviewed this letter to confirm the existing functionality of the time delay relays, and found the documentation acceptable (see safety evaluation supporting Amendment No. 149, January 18, 2007). Thus, the NRC staff concludes, based on those recent test results, that the proposed STI increase will remain consistent with the defense-in-depth philosophy.
Based on the technical evaluation delineated in Sections 3.1 - 3.4 above, the NRC staff finds it acceptable to replace SRs 3.3.5.1.2 and 3.3.5.1.4 for the subject three LPCI loop select logic functions with SRs 3.3.5.1.7 and 3.3.5.1.9, respectively, requiring a channel calibration and logic system functional test every 24 months. In addition, as delineated in Section 3.3 above, the allowable values associated with the three loop select logic functions can be changed as proposed by the licensee.
3.5 Summary of Technical Evaluation Based on the considerations discussed above, the NRC staff finds that the proposed surveillance test interval increase to 24 months for the LPCI loop select time-delay relays is acceptable. The proposed change will eliminate unnecessary transients which could occur if the licensee were required to test the time-delay relays at power. Based on evaluation of recent logic system functional test data, the NRC staff concluded that the time-delay relays had functioned adequately. The NRC staff also concluded that in comparison to other delays in the LPCI injection sequence, possible drift in the time-delay relays would result in a minor additional contribution to the overall timing of the LPCI injection sequence. In conclusion, the MNGP TSs may be revised to change SRs.3.5.1.2 and 3.3.5.1.4 for items 2.k, 2.l, and 2.m of Table 3.3.5.1-1 from the current 92 days to 24 months, and the allowable values for the time delay relays may be changed to reflect new allowable values as proposed by the licensee 3.6 Correction of Typographical Error When the MNGP TSs document was converted to the Improved Standard TS format by Amendment No. 146, a typographical error was inadvertently introduced on Page 3.3.5.1-6.
Specifically, a right parenthesis was omitted for superscript (a) of function 1.e. The licensee proposed to correct this typographical error (i.e., changing (a to (a)). The NRC staff finds this correction acceptable.
3.7 Associated TS Bases Changes The licensee provided draft changes to the TS Bases, a licensee-controlled document. The NRC staff reviewed these changes and found the proposed changes consistent with the proposed changes to the TSs.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Minnesota State official was notified of the proposed issuance of the amendment. The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a surveillance requirement. The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The NRC has previously issued a proposed finding that the amendment involves no significant hazards consideration and there has been no public comment on such finding (72 FR 11391). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
6.0 CONCLUSION
The NRC staff has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor: B. Parks C. Doutt G. Singh Date: July 20, 2007
Monticello Nuclear Generating Plant cc:
Jonathan Rogoff, Esquire Vice President, Counsel & Secretary Nuclear Management Company, LLC 700 First Street Hudson, WI 54016 U.S. Nuclear Regulatory Commission Resident Inspector's Office 2807 W. County Road 75 Monticello, MN 55362 Manager, Nuclear Safety Assessment Monticello Nuclear Generating Plant Nuclear Management Company, LLC 2807 West County Road 75 Monticello, MN 55362-9637 Commissioner Minnesota Pollution Control Agency 520 Lafayette Road St. Paul, MN 55155-4194 Regional Administrator, Region III U.S. Nuclear Regulatory Commission Suite 210 2443 Warrenville Road Lisle, IL 60532-4351 Commissioner Minnesota Department of Health 717 Delaware Street, S. E.
Minneapolis, MN 55440 Douglas M. Gruber, Auditor/Treasurer Wright County Government Center 10 NW Second Street Buffalo, MN 55313 Commissioner Minnesota Department of Commerce 85 7th Place East, Suite 500 St. Paul, MN 55101-2198 Manager - Environmental Protection Division Minnesota Attorney Generals Office 445 Minnesota St., Suite 900 St. Paul, MN 55101-2127 Michael B. Sellman President and Chief Executive Officer Nuclear Management Company, LLC 700 First Street Hudson, MI 54016 Nuclear Asset Manager Xcel Energy, Inc.
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